Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
Titus Labienus had shared with Caesar all the troubles of the dark times of Catilina(1) as well as all the lustre of the Gallic career of victory, had regularly held independent command, and frequently led half the army; as he was the oldest, ablest, and most faithful of Caesar's adjutants, he was beyond question also highest in position and highest in honour.
1. Cf. V. V. Transpadanes
As late as in 704 Caesar had entrusted to him the supreme command in Cisalpine Gaul, in order partly to put this confidential post into safe hands, partly to forward the views of Labienus in his canvass for the consulship. But from this very position Labienus entered into communication with the opposite party, resorted at the beginning of hostilities in 705 to the headquarters of Pompeius instead of those of Caesar, and fought through the whole civil strife with unparalleled bitterness against his old friend and master in war.
We are not sufficiently informed either as to the character of Labienus or as to the special circumstances of his changing sides; but in the main his case certainly presents nothing but a further proof of the fact, that a military chief can reckon far more surely on his captains than on his marshals. To all appearance Labienus was one of those persons who combine with military efficiency utter incapacity as statesmen, and who in consequence, if they unhappily choose or are compelled to take part in politics, are exposed to those strange paroxysms of giddiness, of which the history of Napoleon's marshals supplies so many tragi-comic examples.
He may probably have held himself entitled to rank alongside of Caesar as the second chief of the democracy; and the rejection of this claim of his may have sent him over to the camp of his opponents. His case rendered for the first time apparent the whole gravity of the evil, that Caesar's treatment of his officers as adjutants without independence admitted of the rise of no men fitted to undertake a separate command in his camp, while at the same time he stood urgently in need of such men amidst the diffusion--which might easily be foreseen--of the impending struggle through all the provinces of the wide empire. But this disadvantage was far outweighed by that unity in the supreme leadership, which was the primary condition of all success, and a condition only to be preserved at such a cost.
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